Table 4.
Physical properties of the microemulsion systems and sildenafil citrate microemulsion-loaded hydrogel formulations.
| Test | Sildenafil Citrate Microemulsion | Sildenafil Citrate Microemulsion-Loaded Hydrogel | ||
|---|---|---|---|---|
| (IPM System) | (OA System) | (IPM System) | (OA System) | |
| Appearance | White liquid | White liquid | White liquid | White liquid |
| Clarity | Not clear | Not clear | Not clear | Not clear |
| Droplet size (nm) | 450 ± 120 | 525 ± 45 | 461 ± 108 | 619 ± 68 |
| pH | 5.14 ± 0.02 | 4.54 ± 0.03 | 5.27 ± 0.04 | 4.67 ± 0.07 |
| Viscosity (mPa s) | 4569 ± 76 | 1256 ± 55 | 11,997 ± 1465 | 3231 ± 69 |
| Spreadability (g cm s−1) | 12.28 ± 2.35 | 17.65 ± 1.23 | 16.44 ± 2.12 | 19.45 ± 1.62 |
| Swelling index (%) | - | - | 11.0 ± 1.1 | 14.5 ± 1.2 |
All values are the mean ± SD, n = 3–6. IPM: isopropyl myristate; OA: oleic acid.